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The most recent Patterns and Trends survey conducted by the American Society of Retina Specialists indicates the popularity of sutureless vitrectomy systems. More than 50% of surgeons reported that they expect to use sutureless small-gauge vitrectomy systems with limited 20-gauge vitrectomy instrumentation over the next 5 years. As more surgeons become comfortable with the new instrumentation, safety issues regarding small-gauge wounds' sutureless nature persist. Endophthalmitis resulting from the sutureless nature of these incisions remains a cause for concern. A recent study comparing sutured and sutureless vitrectomy techniques concluded that the rate of endophthalmitis after 25-gauge pars plana vitrectomy (PPV) was significantly higher than that after 20-gauge PPV.1
WOUND ARCHITECTURE STUDIES
Concerned by new reports of increasing endophthalmitis, hypotony and choroidal hemorrhage, we designed laboratory studies to replicate the behavior of sutureless incisions in the immediate postoperative period. In early 2006, we ran a series of experiments demonstrating that conjunctival displacement is an inadequate technique to prevent wound contamination by ocular surface fluid. Using India ink as a surrogate for bacteria, we showed sutureless incision and vitreous cavity contamination of eyes that had undergone sutureless vitrectomy in a cadaver model (Figure 1). These incisions were constructed in a straight manner (perpendicular to the scleral surface) and were of 25-gauge caliber.2
Following the introduction and trend toward oblique (angled) incisions, we conducted another laboratory study to examine the wound architecture of these incisions. We segregated groups of incisions in cadaver human eyes based on the extent of trocar and cannula insertion into the scleral substance before vertically turning the trocar to enter the vitreous cavity. Our attempt was also to make biplanar incisions, as they have been considered more competent and show better apposition based on literature from cataract incision studies. These incisions were then processed histologically and examined. To our surprise, we found that even when multiple incisions were made using the same trocar insertion technique, the wound architecture was inconsistent (Figure 2).
INTERNAL DISRUPTION OF OBLIQUE-ENTRY WOUNDS
Another feature of these incisions that was alarming was the disruption of the internal aspect of oblique wounds (Figure 3).3 This was demonstrated consistently across all groups in which we made oblique-entry wounds. It is our reasoning that this disruption is related to the vertical turning of the trocar after its oblique passage when it finally passes into the vitreous cavity. The turning maneuver may be tearing scleral tissue while the tip of the trocar is still in the substance of the sclera. This disruption was more marked in the group in which we had passed instruments through the cannula, thereby manipulating the incision margins to a larger extent. This disruption reduces the effective distance between the ocular surface and the intraocular cavity. It is likely that in the event of marginal postoperative hypotony, or fluctuating intraocular pressure secondary to lid closure and blinking, the oblique incision may allow the entry of ocular surface fluid.
IMAGING LIMITATIONS
Recent work by other investigators on 23- and 25-gauge caliber incisions suggests that oblique sutureless incisions may be more stable as seen on anterior segment optical coherence tomography (OCT). They may also have a lower incidence of leakage as observed on gross examination. It has also been suggested that the angled incisions are safer based on the absence of contamination by India ink.4
Anterior segment OCT images are unable to demonstrate inner wound disruptions as offered by wound histology. Gross leakage is minimized but not eliminated from these incisions. In the period that these incisions are still healing, inoculation of surface pathogens into the vitreous cavity can have catastrophic consequences.
LOW THRESHOLD FOR SUTURES NECESSARY FOR SAFETY
As different sutureless vitrectomy techniques are developed, we will continue to study their architecture, construction and association with postoperative endophthalmitis in detail. In light of these studies and much ongoing work related to sutureless vitrectomy incisions, we are of the view that if sutureless vitrectomy incisions are to be accepted as broadly as clear corneal cataract incisions, they must be safe. If any incision is seen to leak or look unusual at the end of a case, the threshold for placing a suture by the surgeon must be low (Table 1). In a procedure that has been prolonged or required excessive instrument manipulation, again the threshold for placing a suture should be low. This may be especially imperative in a monocular patient undergoing small gauge transconjunctival sutureless vitrectomy.
Jay M. Stewart, MD, is Assistant Professor of Clinical Ophthalmology at the University of California, San Francisco. He reports no financial relationships. He can be contacted via email at stewartj@vision.ucsf.edu.
Ajay Singh, MD is a resident in the Section of Ophthalmology and Visual Sciences at the University of Chicago. He reports no financial relationships. He can be contacted via email at ajay.singh@uchospitals.edu.
Dean Eliott, MD, is Professor of Ophthalmology and Director of Clinical Affairs, Doheny Eye Institute, Keck School of Medicine at USC and is a member of the Retina Today Editorial Board. He may be reached by phone: +1 323 442 6582; fax: +1 323 442 6766; or via e-mail: deliott@doheny.org.
Ingrid U. Scott, MD, MPH, is Professor of Ophthalmology and Public Health Sciences, Penn State College of Medicine, and is a member of the Retina Today Editorial Board. She may be reached by phone: +1 717 531 4662; fax: +1 717 531 5475; or via e-mail: iscott@psu.edu.
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